The long-term goal of the research is to develop fMCG into a technique that can improve clinical assessment of fetal arrhythmia and fetal well-being. The last few years have seen substantial progress toward this goal, as promising results continue to be reported by our group and by others. In several cases of serious fetal arrhythmia, we have already shown that fMCG can improve outcome. However, the total number of cases studied worldwide is small and further technical development in needed. The goal of the present application is to extend the capability of fMCG to make it more similar to postnatal electrophysiological monitoring, and to demonstrate the usefulness of these extensions by applying them in patient studies. The specific aims are as follows. 1. To reduce the ambiguity of fMCG configuration by using knowledge of probe position and orientation to characterize waveform morphology as a function of fetal presentation 2. To improve the sensitivity of fMCG actography, a new method of assessing fetal activity, by combining information from multiple channels 3. To improve fMCG signal quality by developing adaptive filtering methods to compensate for fetal and maternal movement 4. To apply the methods developed in Aims 1-3 to more fully characterize the patterns of fetal heart rhythm, fetal heart rate, and fetal activity in cases of fetal arrhythmia, congenital heart disease, and high-risk pregnancies.